The present invention relates to hanging conveyance equipment and a learning system for learning operating conditions of the equipment in advance.
Japanese Unexamined Patent Publication No. H11-349280 discloses conventional hanging conveyance equipment. This equipment includes a carriage fitted with a work hand, which can move vertically and be positioned horizontally two-dimensionally with respect to it. The work hand can hold a work and move vertically with the work hanging from it. The carriage can run along a path, below which a number of work supports are arranged. The work hand can load and unload each of the work supports.
In this type of hanging conveyance equipment, the carriage can be stopped accurately in the stop position set above each of the work supports. However, if the work supports are installed or fixed at different degrees of accuracy, the work hand of the carriage in each of the stop positions is displaced with respect to the associated work support laterally and/or angularly around a vertical axis. When a work is lowered onto each the work supports, and when the work on each of the work supports is lifted, the position of the work hand may need to be highly precise. In this case, as disclosed in the foregoing publication, amounts of horizontal two-dimensional positioning for the work hand can be preset for each of the work supports. When the work hand is lowered from the carriage in the stop position for the work support, the work hand can be positioned horizontally two-dimensionally with the associated amounts of positioning.
Specifically, in Japanese Unexamined Patent Publication No. H11-349280, with the carriage in the stop position above each of the work supports, the amounts of horizontal two-dimensional displacement of the work hand with respect to the work support are detected. On the basis of the detected amounts, amounts of positioning for the work hand are set for the work support. Accordingly, both when the work on each of the work supports is lifted to be conveyed from it, and when a work is lowered to be supplied to each the work supports, the work hand is positioned with respect to the carriage only on the basis of the associated amounts of positioning.
In this type of hanging conveyance equipment, the work hand is hung from the carriage by belts that can be extended and taken up. It is possible to lift the work on each of the work supports by lowering the empty work hand to a position where the hand can hold the work. The lowered empty hand may be in a horizontal position. It is possible to lower a work with the work hand by lowering the hand to a position where the load can be unloaded. The lowered work hand holding the work may be inclined because of various factors, such as a shift of the center of gravity of the work, different amounts of extension of the belts, and low producing accuracy of the head of the work. The heads of all works may be inclined uniformly and low in producing accuracy accordingly. The inclination of the work hand leads to horizontal two-dimensional displacement of the hand with respect to the work support. It is consequently impossible to lower the work accurately to a predetermined position on the work support only by positioning the work hand with the same amounts when the work is lifted and when the work is lowered.
The object of the present invention is to provide hanging conveyance equipment that can load and unload works safely and accurately by solving the foregoing conventional problem.
According to a first aspect of the present invention, hanging conveyance equipment is provided, which comprises a carriage, a number of work supports and a work hand. The carriage travels along a horizontal travelling path, which has stop positions arranged along it. Each of the work supports is fixed below one of the stop positions. An amount of work-lifting positioning and an amount of work-lowering positioning are set for each of the work supports. The work hand can hold a work hanging from it. The work hand is supported by the carriage in such a manner that the work hand can be positioned horizontally two-dimensionally with respect to the carriage. The work hand can vertically move with respect to the carriage to load a work onto or unload a work from each of the work supports. When the work hand is lowered from the carriage in each of the stop positions to lift a work from the associated work support, the work hand is positioned horizontally two-dimensionally in accordance with the amount of work-lifting positioning for the support. When the work hand is lowered from the carriage in each of the stop positions to lower a work onto the associated work support, the work hand is positioned horizontally two-dimensionally in accordance with the amount of work-lowering positioning for the support.
The work supports may be fixed at low or different degrees of accuracy with respect to the horizontal travelling path, along which the carriage travels. In such a case, when the work hand is lowered to a position over each of the work supports to load or unload the support, the hand might otherwise be displaced horizontally two-dimensionally with respect to a fixed position on the support. The displacement would make it impossible to place a work in the fixed position on the work support, or to normally lift a work supported in the fixed position.
As stated already, an amount of work-lifting positioning and an amount of work-lowering positioning are set for each of the work supports. When the work hand is lowered from the carriage in each of the stop positions to lift a work from the associated work support, the work hand is positioned horizontally two-dimensionally in accordance with the amount of work-lifting positioning for the support. When the work hand is lowered from the carriage in each of the stop positions to lower a work onto the associated work support, the work hand is positioned horizontally two-dimensionally in accordance with the amount of work-lowering positioning for the support. There may be a case where the empty work hand is lowered to a position over one of the work supports to lift a work from the support, and where the work hand holding a work is lowered to a horizontally two-dimensionally different position over the same support. Even in this case, the work hand can be lowered safely and securely or reliably.
After the empty work hand is lowered, it can hold a work and then be lifted without problems. When the work hand holding a work is lowered so that the work can be placed on each of the work supports, the hand and work may be inclined due to various factors as stated earlier. The inclination would otherwise displace the work horizontally two-dimensionally with respect to the work support. However, the work hand is positioned in accordance with the associated amount of work-lowering positioning so that the inclined work can be placed accurately in the fixed position on the work support.
The amount of work-lowering positioning for each of the work supports may be the associated amount of work-lifting positioning corrected with an amount of correction equivalent to the error between the position of the work hand holding a work and lowered to a predetermined height over the work support and the position of the hand lowered to the height without holding a work. This obviates the need to find both the amount of work-lifting positioning and the amount of work-lowering positioning for each of the work supports by a learning process or the like. Consequently, the time and labor required for the learning process etc. are reduced, and it is easy to operate the conveyance equipment.
The work hand may be positioned with respect to the carriage in parallel with the horizontal travelling path, laterally at right angles to the path and angularly around a vertical axis. In practice, however, if the carriage can stop accurately in the stop positions, the work hand does not need to be positioned in parallel with the travelling path. In other words, practically, the work hand may be positioned with respect to the carriage only laterally at right angles to the travelling path and angularly around the vertical axis. This simplifies the structure of the work hand positioner necessary for the carriage and facilitates the positioning control.
The hanging conveyance equipment needs to learn an amount of horizontal two-dimensional displacement of the work hand relative to each of the work supports at the time when the carriage stops in the associated stop position. The learned amount of displacement is the basis for setting the associated amounts of work-lifting positioning and work-lowering positioning.
According to a second aspect of the present invention, there is provided a learning system suitable for such learning. The learning system can be used with the hanging conveyance equipment to learn an amount of horizontal two-dimensional displacement of the work hand with respect to each of the work supports at the time when the carriage is in the associated stop position. The learning system comprises a first jig, a second jig and a means of displacement operation. The first jig can be placed in the fixed positions on the work supports and has a fixed position on it. The second jig can be placed in the fixed position on the first jig and includes a held part for engaging with the work hand to be held by it. One of the jigs includes a detected part. The other jig includes a detector for detecting the horizontal two-dimensional position of the detected part to find reference position data for the detected part with the second jig placed in the fixed position on the first jig and comparative position data for the detected part with the second jig held by the work hand of the carriage in each the stop positions and lowered onto the first jig. The means of displacement operation finds an amount of horizontal two-dimensional displacement of the work hand with respect to each of the work supports from the reference position data and the associated comparative position data.
The learning system makes it possible to detect the necessary amounts of displacement accurately and easily only by means of the two jigs without providing a special detected part and a special detector for learning on the work hand and the existing work supports.
The amount of displacement for each of the work supports is detected with the second jig held by the work hand and placed on the first jig set on the work support. Consequently, in comparison with a case where the displacement of the work hand would otherwise be detected with the hand in its top (home) position over the work support, the learning system makes the detection reliable even if, when the work hand is lowered, it inclines due to different amounts of extension of the belts with which the hand hangs. This makes it possible to detect amounts of displacement that can be used to set amounts of positioning fit for loading and unloading operations, which are performed by actually lowering the work hand.
In practice, as stated earlier, the work hand does not need to be positioned in parallel with the horizontal travelling path if the carriage can stop accurately in the stop positions. Consequently, the amount of horizontal two-dimensional displacement of the work hand found for each of the work supports by the means of displacement operation (the operation/recording/transmission processor 56 in the embodiment of the invention) may consist of an amount of lateral displacement of the hand at right angles to the travelling path and an amount of angular displacement of the hand around a vertical axis.
The detector may be an image pickup camera fitted to the first jig and facing upward. The detected part may be a mark placed on the second jig near the held part and facing downward. The first jig to which the camera is fitted can be set on each of the work supports. The second jig on which the mark is placed can be held by the work hand and vertically moved. In this case, as compared with a case where the camera would otherwise be fitted to the second jig and where the mark would otherwise be placed on the first jig, the wiring between the camera and the means of displacement operation is easy, and the camera is safe against damage. If the mark is placed on the second jig near the held part, which can be held by the work hand, the displacement detection is accurate. The first jig to which the camera is fitted can be used for a process of learning amounts of work-lowering correction, as stated in the embodiment of the invention.
The first jig may be fitted with a number of removable positioning pins on its top. The second jig may be formed with positioning holes in its bottom, each of which can engage with one of the pins. This improves the positional accuracy of the second jig in the detection of reference position data. However, this exerts no influence on the position of the second jig when this jig is held by the work hand and placed on the first jig in the detection of comparative position data. Consequently, the displacement detection is accurate.
Before operating the hanging conveyance equipment, it is necessary to find the amounts of work-lowering positioning by means of a second learning system for finding an amount of horizontal two-dimensional displacement of the work hand lowered with a work.
The horizontal travelling path may further have a tentative stop position set in it. The second learning system may include a tentative port for exclusive use with a learning process for finding an amount of work-lowering correction. The tentative port is fixed below the tentative stop position. The tentative port has a fixed position set on it at the same height as the fixed positions of the work supports are set. A learning work can be placed in this fixed position and is fitted with a detected part on its bottom. The tentative port is fitted with a second detector under its fixed position for detecting the detected part of the learning work. The second learning system may further include a second means of displacement operation for finding, from reference position data obtained by the second detector detecting the detected part of the learning work placed in the fixed position on the tentative port and comparative position data obtained by the second detector detecting the detected part of the learning work held by the work hand of the carriage in the tentative stop position, an amount of horizontal two-dimensional displacement of the work hand lowered with the learning work.
The second learning system makes it possible to easily and accurately perform the learning process for finding an amount of work-lowering correction. The costs of this learning system can be reduced if it includes the first jig fitted with the detector, which may be an image pickup camera, for use with the learning process performed for each of the work supports, as stated in the embodiment of the invention.
Actual or practical hanging conveyance equipment according to the present invention includes a number of carriages 5 supported movably along a horizontal path. This equipment also includes work hands 8 each supported by one of the carriages 5 vertically and horizontally movably with respect to it. The equipment further includes a number of work supports 3 fixed below the horizontal path.
According to a third aspect of the present invention, there is provided a learning method suitable for this hanging conveyance equipment. The learning method comprises the steps of:
choosing a reference carriage 5S from the carriages 5 and a reference work support 3S from the work supports 3;
performing a first learning process for finding a first amount of horizontal two-dimensional positioning for the work hand 8 of the reference carriage 5S with respect to each of the work supports 3;
storing the first amounts of positioning with respect to the work supports 3 as unified amounts of positioning in the carriages 5 other than the reference carriage 5S;
performing a second learning process for finding a second amount of horizontal two-dimensional positioning for the work hand 8 of each carriage with respect to the reference work support 3S;
performing a comparison operation of the unified and second amounts of positioning for each of the carriages 5 to find an amount of correction exclusive to each of the carriages 5 and common to all of the work supports 3; and
correcting the unified amount of positioning for each of the work supports 3 with the amount of correction.
The learning method obviates the need to perform learning processes for all of the carriages with respect to each of the work supports. Even if the carriages differ in producing accuracy, the learning method makes it possible to very accurately set an amount of positioning for the work hand of each of the carriages with respect to each of the work supports.
Other characteristics and/or features of the present invention will be understood easily from the following description of preferred embodiments of the invention with reference to the accompanying drawings.